Download normal limits for the qt interval in children

NORMAL LIMITS FOR THE QT INTERVAL IN CHILDREN
I. Kisileva,PhD, L.Makarov*, MD, V.Dolgikh**,MD, A.Bimbaev, PhD, T.Bairova***, PhD.
Childrens hospital of Respublic Buryatia (Ulan Ude, Russia), *Dpt. of Diagnostic of Arrhythmias, Russian
Center for children arrhythmias, Moscow Institute of Pediatrics and Children Surgery (Moscow, Russia),
**Institute of Pediatrics and reproduction (Irkutsk, Russia), ***Buryats branche of the Scientific Center
of Medical ecology (Ulan-Ude, Russia)
Contacts: Prof. L.Makarov Moscow Institute of Pediatrics and Children Surgery, 125412 Taldomskaua
str.2 , Moscow, Russia. E mail: [email protected]
Abstract: The aim of this study was to
determine the normal limits for QT interval in
children 0-17 years. For 1531 children aged 0 to
17 years (8,6 ± 10,2) a 12-lead rest ECG was
recorded and measured, separately Slavs and
Buryats. The QT and QTc by Bazzet’s formula
were calculated separately for B and G.
Significant differences were not shown to exist
in different ethnic groups. Significant sex
differences could be demonstrated only for
maximum QTc duration. It was revelead that
normal limits for the QTc interval in children
does not depend on gender. Upper limit of QTc
for children 1-7 years old was 443 ms for boy
and girls. In children 0-1 and 8-17 years old
upper limit of the QTc is significant higher in
girls (till 471 ms). Lowest limit (2 percentile) of
the QTc is 330 ms and has not differences in age
and
sex.
INTRODUCTION: A number of diseases
with high risk of sudden death (SD) has
expressed ethnic predisposition, arising
mainly in the certain ethnic groups, often
prediminantely in Asia region /1/.
Prolongation or shortening of the QT
interval are one of the most authentic risk
factors
for
dangerous
ventricular
arrhythmias /2,3/. However, little is known
about normal limit for QT interval in
children, especially in different ethnic
groups. The aim of the present study was to
define normal limits of the QT interval
among the children and adolescents 0-17
years old in slavic and Buryat population.
METHOD:
Cross research within the framework of the
All-Russia
prophylactic
medical
examination is carried out. Representative
sample of children in 2000 children 0 - 17
years old was created. Children with
previously known cardiovascular diseases
(gongenital and aguired heart diseases,
evidence cardiac arrhythmias) were exluded
from the study. The ratio of children of a
slavic and Buryat (mongolian ethnic type
lived in area of Baikal lake and Siberia)
nationality were 57,3 % to 42,7%
accordingly. 12 channel rest ECG is carried
out at 1531 children (76,6% from sample,
0,57 % of all children living in Respublic
Buryatia). There were 47,2% girls (G) and
52,8% - boys (B), 69,2% of city and 30,8%
of rural children. Recordings ECG were
made using three or single channel systems
(50 mm/sec, 10 mm/mV). Interval QT was
measured manually in II standard lead. The
normal limits of the heart rate (HR bpm),
QT interval (ms) and corrected QT (QTc) by
formula Bazett (that presented in /4/ as QT
interval divided by the square root of the
preceding RR interval) was established for
seven age groups, separately for B and G.
Average RR interval from recorded strip
was used for calculation and assessment of
the QTc interval.
RESULTS.
Received values of the HR (bpm), QT and
QTс intervals (medians, 2nd and 98th
percentile) in children and adolescents 0-17
years old are presented in the Table. QT
interval had tight connection with HR (r0,98, p < 0.001) and age (r 0,98, p < 0.001).
As a whole in all group, authentic
distinctions depending on a gender are
marked for maximal values QTс: 438,3 ±
8,4 ms for B and 454,1 ± 15,2 ms for G (р =
0,037), firstly in children 8 - 17 years.
Values QTс > 440 ms were revealed at 41
children (2,3 % or 1:37); > 460 ms - at 16
(1,05 % or 1:96); > 480 ms - at 4 (0,26 % or
572
1:383) surveyed, more often in G (1,66 %
and 0,49 % accordingly G and B, p < 0,05),
is especial in the age of 8-15 years (83,3 %)
and doubtfully was registered in the Buryat
population than in slavic (0,46% vs 0,11 %).
32,3 ms vs 342,3 ± 12,7 ms accordingly).
Several other potentially proarrhythmogenic
“microanomalous” of ECG was revealed in
4 from 8 children with shortening of the QT
interval, such as ST elevation, epsilon wave
(eW) in V1-V2. (Fig).
Table
Age
(years
-old)
Heart rate
(beat/min)
QT (ms)
QTc (ms)*
0-1
131
105
–198
136
102
–197
281
223
–
304
287
208
–
295
400
333 –
451
400
344 –
462
1-2
120
85 –
187
126
88 –
175
295
239295
278
236
–317
420
349 –
443
387
346 –
443
3-4
99
78 –
120
100
77 –
150
308
258
–337
319
256
–367
390
347423
400
351 –
442
5-7
89
67123
90
64120
317
265–
389
305
268–
356
383
326–
442
381
330–
431
8-11
78
54 –
108
80
58 –
117
337
289
–
396
338
297
–
397
378
345 –
436
395
338 –
466
12-15
73
48 –
103
79
53 –
116
345
296
–
425
367
287–
438
390
337 –
440
403
350 –
471
16-17
70
48 –
102
72
53111
337
304–
417
357
317436
380
331–
436
396
349464
Boys
Girls
Boys
Girls
Boys
Girls
* QTc= QT interval divided by the square root
of the preceding RR interval
All children with the maximal values of the
QT interval had no syncope or family
history of SD. Shortening of the QTc lower
than 2 percentile (350 ms) was revealed at
12 (0,78 %) children, 9 B and 3 G 3 - 16
years (11,2 ± 4,2). Average QTc in this
groupe was 334 ± 27,4 ms. At 8 of them
(66,7 %) had syncope, or presyncope in the
history and/or cases of SD in family history.
QTс was nonsignificantly shorter at children
with a syncope and family history of SD
than at children without symptoms (329,1 ±
Fig. Short QT interval in 16 year-old boys
(I,II,III, V1-V3 leads): HR 58 bpm (RR 1,03 sec),
QT 340 ms, QTc - 335 ms. Saddle-back type ST
elevation and eW in V1-V2. Family history:
sudden death in grandfather (58 year), two
uncles (50 and 38 year, both during night) and
aunt (35 year, during night).
We selected two degrees of shortening of the
QT interval in children by our results: first
degree – of QTс < 350 ms (15,2 % in
population)and second degree - QTс < 330
ms (0,72% in population). We compared of
received results with the most known data
ECG investigations in children (2141 white
children in the Canadian /6/ and 1912
children in Dutch /7/ population). Normal
limits for HR and maximum QTc in our
study have not differences from limits
presented A.Davignon /6/ and P.Rijnbeek
/7/. The minimum level of the absolute QT
interval received by us were comparable to
data A. Davignon et al /6/, but it is
substantially lower, than in research of P.
Rijnbeek et al /7/. At identical values HR
limits in ours and these researches, this
distinction can be caused by some
differences in measurement of QT (probably
a choice representative RR interval at
presence sinus arrhythmia). Other factors
also may play a role, first of all
573
antropometric changes, would reguare a
futher studies.
CONCLUSIONS.
Normal limits for the QTc interval in
children not have ethnic differences in slavic
and Buryat population. QTc for children 1-7
years old not exceed 445 ms and does not
depend of gender and age. In children 0-1
and 8-17 years old QTc is significant longer
in G than in B (471 vs 442 ms). Two
degrees of shortening of the QT interval in
children could be established: QTс < 350 ms
(1th degree, 15,2 % in children population)
and QTc < 330 ms (2 th degree, 0,72 % in
children population). Prolongation of the QT
interval as well as shortening needs
excluding of diseases with high risk of SD
(long QT, Brugada, idiopathic short QT
syndromes, arrhythmogenic right ventricular
dysplasia and other) by Holter monitoring,
treadmill test, drug test, EP study, possibly
molecular-genetic study.
7. Rijnbeek PR, Witsenburg M, Schrama
E, Hess J, Kors JA. New normal limits
for the paediatric electrocardiogram.
Eur Heart J. 2001 Apr;22(8):702-11.
References:
1. Nademanee K. Sudden Unexplained
Death Syndrome in Southeast Asia.
Am J Cardiol 1997;79(6A): p10-11
2. Moss A. The Long QT interval
syndrome. The American Journal of
Cardiology 1997; 20:p.17-19.
3. Gussak I, Brugada P, Brugada J, Wright
RS, Kopecky SL, Chaitman BR,
Bjerregaard P. Idiopathic short QT
interval: a new clinical syndrome?
Cardiology 2000;94(2):99-102
4. Taran L., Szilagy N. The duration of
electrical systole (QT) in acute
rheumatic carditis in children. Am Heart
J. 1947;33:14-26
5. Rautaharju P., Zhou S., Wong S.,
Caihoun H., Berenson G., Prineas R.,
Davington A. Sex differences in the
evolution of the electrocardiographic QT
interval with age. Can J Cardiol
1992;8:690-695
6. Davignon A., Rautaharju P., Boisselle
E., Soumis F., Megelas M., Choguette
A. Normal ECG standards for infants
and children. Pediatric Cardiology
1979/1980; 1: 123-131
574